Device and method for channel access in wireless communication system

A method performed by a user equipment (UE), in a wireless communication system, comprising:

• performing a channel access procedure for a channel occupancy time (COT) in an unlicensed band;
• obtaining a hybrid automatic repeat request-acknowledge (HARQ-ACK) feedback for a reference duration based on the channel access procedure, wherein the HARQ-ACK feedback comprises a transmission result for at least one code block group (CBG) transmitted on a physical uplink shared channel (PUSCH) or at least one transmission result for at least one transport block (TB) transmitted on at least one PUSCH;
• in case that a ratio of ACKs for the at least one CBG is greater than a threshold based on the HARQ-ACK feedback, identifying a size of a contention window for a next channel access procedure as a minimum size;
• and
• in case that the at least one transmission result for the TB in the reference duration corresponds to at least one ACK, identifying the size of the contention window as the minimum size,
• wherein the reference duration comprises a first slot where the at least one PUSCH is transmitted after the COT is started, the COT being initiated by a base station.

A base station, in a wireless communication system, comprising:

• at least one transceiver;
• and
• at least one processor,
• wherein the at least one processor is configured to:
• perform a channel access procedure for a channel occupancy time (COT) in an unlicensed band;
• obtain a hybrid automatic repeat request-acknowledge (HARQ-ACK) feedback for a reference duration based on the channel access procedure, wherein the HARQ-ACK feedback comprises a transmission result for at least one code block group (CBG) transmitted on a physical downlink shared channel (PDSCH) or at least one transmission result for at least one transport block (TB) transmitted on at least one PDSCH;
• in case that a ratio of ACKs for the at least one CBG is greater than a threshold based on the HARQ-ACK feedback, identify a size of a contention window for a next channel access procedure as a minimum size;
• and
• in case that the at least one transmission result for the TB in the reference duration corresponds to at least one ACK, identify the size of the contention window as the minimum size,
• wherein the reference duration comprises a first slot where the at least one PDSCH is transmitted after the COT is started, the COT being initiated by the base station.

A user equipment (UE), in a wireless communication system, comprising:

• at least one transceiver;
• and
• at least one processor,
• wherein the at least one processor is configured to:
• perform a channel access procedure for a channel occupancy time (COT) in an unlicensed band;
• obtain a hybrid automatic repeat request-acknowledge (HARQ-ACK) feedback for a reference duration based on the channel access procedure, wherein the HARQ-ACK feedback comprises a transmission result for at least one code block group (CBG) transmitted on a physical uplink shared channel (PUSCH) or at least one transmission result for at least one transport block (TB) transmitted on at least one PUSCH;
• in case that a ratio of ACKs for the at least one CBG is greater than a threshold based on the HARQ-ACK feedback, identify a size of a contention window for a next channel access procedure as a minimum size;
• and
• in case that the at least one transmission result for the TB in the reference duration corresponds to at least one ACK, identify the size of the contention window as the minimum size,
• wherein the reference duration comprises a first slot where at least one PUSCH is transmitted after the COT is started, the COT being initiated by a base station.